COMP 101 Introduction

The Team

Enrolling

The Website

The Class

How a Computer Works It is actually a very simple machine: It executes exactly what it is told to do Rather like Forrest Gump

Seriously, … Computers Execute algorithms Need to be told what to do And to whom to do it

Algorithm Just a recipe What do recipes do? Steps Tests Repetitions

Internet

What is the Internet? The machines The connections The content

The Internet in 1980

The Internet Circa 1998

What made the Internet succeed? Early users shared information Command lines 1993: Browser invented! Mosaic Marc Andressen Brought Graphical Interface Easy access No technical skill needed

Browsers

Viewing a Web Page Server Web Server Pages SERVER web page repository WEB PAGE instructions stores information and instructions BROWSER retrieves web page and follows instructions 2 1 3 Client Browser

Viewing a Web Page Server Web Server Pages SERVER web page repository WEB PAGE instructions stores information and instructions BROWSER retrieves web page and follows instructions 2 1 3 Client Browser

What is http and https? HyperText Transfer Protocol Protocol: set of rules Transfer: move it from one place to another Hypertext: the essence of the web – the links HTTPS is the secure version Tells the browser that it has to go to the internet to find it

Retrieving a web page That’s a file You type the URL How does your computer find it? Up to the first slash is the SERVER name Everything after that is folders until the last one That’s a file

Routing: Getting to the Server Server names don’t tell me where anything is They DO tell me who gave them the name cs.unc.edu: organization that manages edu gave the university unc Unc gave the department cs Translate the name to a number called the IP address Example: 149.72.62.234 Each value ranges from 0 to 255! Translation is done through a table called the Domain Name System (DNS)

Browser Instructions

What do the instructions look like Open Chrome We want to look at a page View Page Source Only TEXT Even though the page has a picture on it!

Web Instructions: Three Legs HTML Content CSS Presentation JavaScript Behavior

Creating HTML All we have to do is edit a page CANNOT use a word processor Word, Pages, Writer Why? They add all sorts of gorp Do NOT need special software We WILL use it: Komodo Editor It HELPS